1. Field of the Invention
The present invention relates to a phase compensation circuit of a voltage regulator and reduction in power consumption thereof.
2. Description of the Related Art
As a conventional voltage regulator that stably operates regardless of output capacity or output resistance, the circuit illustrated in FIG. 6 has been known.
The conventional voltage regulator is constituted of a reference voltage circuit 101, a differential amplifier circuit 102, a PMOS transistor 106, a phase compensation circuit 460, resistors 108 and 109, a ground terminal 100, an output terminal 121, and a supply terminal 150. The phase compensation circuit 460 is constituted of a constant current circuit 405, NMOS transistors 401, 406, 403 and 408, a capacitor 407, and a resistor 404. The differential amplifier circuit 102 is constituted of a one-stage amplifier illustrated in FIG. 7.
Regarding the connection, an inverting input terminal of the differential amplifier circuit 102 is connected to the reference voltage circuit 101, a non-inverting input terminal thereof is connected to a connection point of the resistors 108 and 109, and an output terminal thereof is connected to the gate of the PMOS transistor 106 and the drain of the NMOS transistor 401. The other end of the reference voltage circuit 101 is connected to the ground terminal 100. The source of the NMOS transistor 401 is connected to the drain of the NMOS transistor 403, and the gate thereof is connected to the gate and the drain of the NMOS transistor 406. The source of the NMOS transistor 403 is connected to the ground terminal 100, and a gate thereof is connected to the resistor 404 and the drain of the NMOS transistor 408. The source of the NMOS transistor 408 is connected to the ground terminal 100, the gate thereof is connected to the other end of the resistor 404 and the capacitor 407, and the drain thereof is connected to the source of the NMOS transistor 406. The drain of the NMOS transistor 406 is connected to a constant current circuit 405, and the other end of the constant current circuit 405 is connected to the supply terminal 150. The source of the PMOS transistor 106 is connected to the supply terminal 150, and the drain thereof is connected to the output terminal 121, the other end of the capacitor 407, and the other end of the resistor 108. The other end of the resistor 109 is connected to the ground terminal 100 (refer to, for example, non-patent document 1).